Mercury switch



March I 13, 1934. F. MOOS 1,951,161

MERCURY SWITCH Filed Feb. 20, 1950 1 g, INVE2T%W B I I ms ATTORNEY.

Patented Mar. 13,

UNITED STATES PATENT OFFICE 1,951,161 A MERCURY swrrcn ApplicationFebruary 20, 1930, Serial No; 429,861 3 Claims. (01. 200-152) Thepresent invention relates to electric switches of the fluid flow type,and particularly to switches having soft glass envelopes.

. The invention consists in a new method and in 5 a new and novelcombination of parts as hereinafter set forth and claimed.

A particular object of the invention is to pro duce a fluid flow switchhaving a soft glass en velope which will not only be inexpensive butreliable and which will have a long useful life. Another object of theinvention is to provide an inlead for such a switch'whichwillbe'relatively simple and inexpensive. Still another object of theinvention is to provide a switch which will be sensitive to slightchanges in the fluid level therein. Other objects and advantages of theinvention will appear from the following detailed specification, or froman inspection of the accompanying drawing.

From the manufacturing standpoint the use of soft glass for theenvelopes of mercury or other fluid flow switches is highly desirable,since it is relatively inexpensive and is easily worked. Several factorshave, however, tended to mini mize the use of this material. One ofthese has been the fact that no simple, inexpensive inlead constructionhas heretofore been possible, especially where appreciable currents wereto be interrupted. Platinum is too expensive for inleads having anyappreciable current capacity; dumet is somewhat expensive and has thefurther dis-= advantage that in switches containing mercury it has beenfound expedient in some instances to either weld it to an electrode ofdifferent metal or else remove the copper sheath from the portionextending within the envelope; while other metals, such as tungsten,which have heretofore been used for inleads could not be convenientlysealed into soft glass. Furthermore, the life of such a switch has beenuncertain since any areing in the switch in proximity to the soft glasswall is apt to completely destroy the switch. Certain remedial measures,some involving the use of shields of hard glass, fused silica, or thelike, have heretofore been adopted, particularly in switches in whichthe circuit was made and broken between liquid electrodes, but the addedexpense has been a limiting factor in their use. Ihave discovered thatboth of these difliculties may be overcome by the use of chrome-ironinleads, suitably placed in the envelope, whereby a relatively cheapfluid switch of great reliability and having a long useful life isproduced. The

chrome-iron alloy which is used for the inlead material is sealed intothe soft glass envelope in a cury switch of t e tilting type in a closedcircuit novel'manner of my invention, the inleads being so disposedwithin the envelope that a fluid pool always shields the adjacentportion of the soft glass envelope from the arcing which may occur whenthe circuit is either closed or interrupted. The method of sealing thechrome-iron inleads into the soft glass envelope according to myinvention is extremely-simple, in that the inlead may be sealed directlyinto a lime glass envelope, or where the envelope is of lead glass theinlead need only have a lime glass, instead of the usual lead glass,head or ring fused thereto before sealing into said envelope. My newar-= rangement of elements, which consists in placing at least one ofthe electrodes at some distance to from the end of the envelope and somedistance from the bottom thereof, in a switch of the tilting type, iscontrary to what has been considered the best practice in mercuryswitches, since it requires the use of more mercury, but I have foundiii that this new arrangement is very effective in protecting theenvelope. In mercury switches the use of chrome-iron inleads, due to thefact that the mercury does not tend to amalgamate there= with or adherethereto, permits the construction tilt of a switch of this type whichwill be extremely sensitive to small changes in mercury level, a resultwhich is impossible with other known inlead materials without renderingthe protection of the walls by the mercury uncertain.

For the purpose of illustrating my invention I have shown one embodimentthereof in the accompanying drawing, in which Fig. l is a longitudinalcross section of a merposition,

Fig. 2 is a similar view of the same switch at the instant of opening,and

Fig. 3 is a longitudinal cross-section showing a detail of the inleadseal used in this switch.

In the drawing a tubular soft glass envelope 1, which is preferablyfilled with hydrogen or the like, has inleads 2 and 3 of suitablematerial, such as chrome-iron alloy, sealed through the top thereoftoward one end of said envelope.

I have found the chrome-iron alloy which is sold by the Crucible. SteelCo. of America under the trade name of Stainless Iron 23/30 ChromeAnnealed to be especially suitable for these electrodes, although othersimilar alloys having a coeflicient of expansion not materially greaterthan that of soft glass and having the property of not amalgamating withmercury can be used in place thereof.

A body of mercury 4 in said envelope 1 is adapted 110 to close thecircuit between said electrodes when the envelope 1 is in the positionindicated in Fig. 1. The inlead 2 is located at an appreciable distance,of say atleast the radius of the envelope 1, from the end of saidenvelope and while it extends downwardly toward the bottom of saidenvelope, terminates at a considerable distance thereabove. The inlead 3is located at any suitable distance from the inlead 2, and extendssubstantially to the bottom of the envelope 1, the lower end thereofpreferably being pointed or flattened'so as not to impede the free flowof the mercury 4 thereby. The position of the inlead 3 may be variedconsiderably, however, so long as it makes contact before inlead 2, andmaintains contact longer, with the mercury 4 when the switch is tiltedbetween the positions of Figs. 1 and 2.

As shown in Fig. 3, the seal between envelope 1 and the inleads 2 and 3,when said envelope is of lead glass and said inleads are of chrome-iron,is effected by fusing a bead 5 of lime glass to said inleads, and thenfusing said envelope to said head.

In the use and operation of the switch, the switch being in the positionshown in Fig. 1 a circuit will be completed by the mercury 4 between theinleads 2 and 3. As the switch is tilted toward the position shown inFig. 2 the mercury 4 will decrease in depth until it finally opens thecircuit at inlead 2. At this moment the mercury 4 still extends to theadjacent end of the envelope 1, hence the bottom of said envelope, whichis the only part thereof in proximity to the arc of rupture, iscompletely shielded thereby from thearc. Since the arc can thus have nodeleterious eflect on the envelope 1, it follows that the switch has anextremely long useful life. This result may also be achieved wheninleads which are wet by mercury after amalgamation therewith are used,but only by considerable sacrifice in the sensitivity of the switch.

While I have shown and described a specific embodiment of my inventionit is obvious that my invention is not limited thereto. It is further tobe understood that various changes, omissions and substitutions may bemade therein without departing from the spirit of my invention.

What is claimed is:

'1. In an electric fluid flow switch of the tilting type, an elongatedtubular sealed vitreous envelope, a conducting fluid therein, andinleads to which mercury will not adhere sealed into said envelope andextending into said fluid when said switch is in a closed circuitposition, one of said inleads being at a distance from the end of saidenvelope which is at least equal to the distance from the side walls ofsaid envelope, and terminating at an appreciable distance from thebottom of said envelope, and another inlead so located as to be incontact with said fluid before said circuit is made and after it isbroken at first said electrode, said fluid being suflicient in quantityto form a shield between arcs at first said electrode and the bottom ofsaid envelope.

2. In an electric fluid flow switch of the tilting type, an elongatedtubular sealed vitreous envelope, mercury therein, and inleads of achrome iron alloy which is not wetted by mercury sealed into saidenvelope and extending into said fluid when said switch is' in a closedcircuit position, one of said inleads being at a distance from the endof said envelope which is at least equal to the distance from the sidewalls of said envelope, and terminating at an appreciable distance fromthe bottom of said envelope, and another inlead so located as to be incontact with said fluid before said circuit is made and after it isbroken at first said electrode, said fluid forming a shield between arcsat first said electrode and the bottom of said envelope.

3. In an electric fluid flow switch of the tilting type, anelongated-tubular sealed vitreous envelope of soft glass, mercurytherein, and inleads of a chrome-iron alloy which is not wetted by 110mercury sealed into said envelope and extending into said fluid whensaid switch is in a closed circuit position, one of said inleads beingat a distance from the end of said envelope which is at least equal tothe distance from the side walls of 115 said envelope, and terminatingat an appreciable distance from the bottom of said envelope, said inleadhaving a smooth surface to which mercury will not adhere, and anotherinlead so located as to be in contact with said fluid before said 120circuit is made and after it is broken at first said electrode, fluidbeing suflicient in said quantity to form a shield between arcs at firstsaid electrode and the bottom of said envelope.

FRANK MOOS.

